Weight loss surgery (Bariatric surgery)
Weight loss surgery (Bariatric surgery)

Weight loss surgery, also called bariatric surgery, is used as a last resort to treat people who are dangerously obese (carrying an abnormally excessive amount of body fat).

This type of surgery is only available on the NHS to treat people with potentially life-threatening obesity that will not respond to non-surgical treatments, such as lifestyle changes.

In Wales the Welsh Health Specialised Services Committee has produced a policy document which applies to all seven Health Boards in Wales.

The policy says that individuals must satisfy all elements of the access criteria for assessment and treatment to proceed.




The access criteria for specialised bariatric services are set out below:

  • The individual is aged 18 years or over;
  • The individual has a BMI of 40 or greater;
  • Morbid/severe obesity has been present for at least five years;
  • The individual has received, and complied with, an intensive weight management programme at a multi-disciplinary weight management clinic (level 2/3 of the All Wales Obesity Pathway) for at least 24 months duration, but has been unable to achieve and maintain a healthy weight; and
  • The individual is approved for surgery by the bariatric MDT at the Welsh Institute of Metabolic and Obesity Surgery, Abertawe Bro Morgannwg University Health Board.

See below for information on how to calculate your BMI.

For people who meet the above criteria, weight loss surgery has proved to be effective in significantly and quickly reducing the amount of excess body fat.

However, it's always recommended that you try to lose weight through a healthy, calorie-controlled diet and increased amounts of exercise before you consider weight loss surgery, as surgery carries a risk of complications and requires a significant change in lifestyle afterwards.

Because of the risks associated with weight loss surgery, most surgeons, whether they are working privately or for the NHS, would only consider a person for surgery if there was a clinical need, and not just for cosmetic reasons.

For more information, see Weight loss surgery - who can have it.

Availability of weight loss surgery

Even if you are eligible for weight loss surgery, the demand for this surgery on the NHS is currently higher than the supply in many areas of the country. Therefore, there may be a considerable waiting list.

Weight loss surgery is also available privately. Prices are around:

  • £5,000-8,000 for gastric banding
  • £9,500-15,000 for gastric bypass surgery

An increasing number of people are seeking treatment abroad as costs for private treatment are often cheaper in other countries, but this option should be considered carefully. For more information, see Planned treatment abroad.

Types of weight loss surgery

The two most widely used types of weight loss surgery are:

  • gastric band, where a band is used to reduce the size of the stomach so a smaller amount of food is required to make you feel full
  • gastric bypass, where your digestive system is re-routed past most of your stomach so you digest less food and it takes much less food to make you feel full
  • sleeve gastrectomy – where some of the stomach is removed to reduce the amount of food that's required to make you feel full

Several other surgical techniques may be recommended in certain circumstances.

For more information, see Weight loss surgery - how it is performed.

Life after weight loss surgery

Weight loss surgery can achieve impressive results in terms of the amount of weight lost, but it shouldn't be seen as a magic cure for obesity.

People who have had weight loss surgery need to stick to a rigorous and lifelong plan afterwards to avoid putting weight back on or long-term complications.

This plan will include:

  • a carefully controlled diet
  • regular exercise

The rapid weight loss may cause relationship problems – for example, with a partner who is also obese – and it may lead to unwanted loose folds of skin, which may need further surgery to correct.

Many people with mental health problems, such as depression or anxiety, find that these problems do not automatically improve because they have lost weight.

It's important to have realistic expectations about what life after weight loss surgery will be like.

Read more about life after weight loss surgery.


As with all types of surgery, weight loss surgery carries the risk of complications, some of which are serious and potentially fatal, such as:

The overall risk of death in hospital after having any kind of weight loss surgery is around 1 in 1,000. Certain risk factors, such as high blood pressure or a BMI of 50 or above, also increase the risk of complications.

For more information, see Weight loss surgery - risks.


As long as a person is willing and able to stick to their agreed plan afterwards, surgery can effectively reduce their weight and treat conditions associated with obesity, such as diabetes.

Recent research carried out in America found that on average:

  • People with a gastric band will lose around half their excess body weight.
  • People with a gastric bypass will lose around two-thirds of their excess body weight.

Both techniques also lead to a considerable improvement (and sometimes a complete cure) of obesity-related conditions, such as diabetes or high blood pressure.

Body mass index and obesity

The most widely used way to measure your size is to calculate your body mass index (BMI). This is your weight in kilograms divided by your height in metres squared:

  • If your BMI is 25-29.9, you are over the ideal weight for your height (overweight).
  • If your BMI is 30-39.9, you are obese.
  • If your BMI is over 40, you are very obese (known as morbidly obese).

BMI does not provide an accurate assessment of weight in all circumstances, such as in people who are very muscular or children going through a sudden growth spurt.

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Who can use it?

In Wales the Welsh Health Specialised Services Committee has produced a policy document which sets out the criteria that need to be fulfilled for an individual to qualify for consederation for Bariatric Surgery. This policy applies to all seven Health Boards in Wales.

The policy says that individuals must satisfy all elements of the access criteria for assessment and treatment to proceed.

The access criteria for specialised bariatric services are set out below:

  • The individual is aged 18 years or over;
  • The individual has a BMI of 40 or greater;
  • Morbid/severe obesity has been present for at least five years;
  • The individual has received, and complied with, an intensive weight management programme at a multi-disciplinary weight management clinic (level 2/3 of the All Wales Obesity Pathway) for at least 24 months duration, but has been unable to achieve and maintain a healthy weight; and
  • The individual is approved for surgery by the bariatric MDT at the Welsh Institute of Metabolic and Obesity Surgery, Abertawe Bro Morgannwg University Health Board.

When weight loss surgery isn't suitable 

Weight loss surgery may not be recommended if you have a serious illness that would not be improved after the operation, such as:

Weight loss surgery is also unlikely to be recommended if a mental health condition or other underlying factor means you'd be unable to commit to long-term follow-up and lifestyle changes.

Examples of these conditions and factors include:

  • schizophrenia for which you are refusing to seek treatment
  • actively abusing alcohol or drugs
  • a previous history of not complying with medical recommendations about your care


Weight loss surgery would only be considered to treat obese children in exceptional circumstances, and only if the child is physically mature (around the age of 13 for girls and 15 for boys).

Most experts in obesity would only recommend surgery as a last resort treatment for children who are severely morbidly obese (a BMI of 50 of above), or who are morbidly obese (a BMI of 40 or above) and also have a serious health condition that would improve if they lost weight.

Read the NICE guidelines on managing overweight and obesity among children and young people.

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Getting Ready

Weight loss surgery and adapting to life after surgery is a challenging process, requiring the input of many different medical professionals working together as a team.

This is known as a multidisciplinary team (MDT) and it may consist of:

  • a surgeon
  • an anaesthetist
  • a dietitian
  • a psychologist
  • a gastroenterologist (doctor who specialises in treating digestive conditions)
  • a specialist weight loss surgical nurse, who will usually be your first point of contact

Most MDTs operate out of specialist bariatric surgery units, which are typically based in larger hospitals.

Before your weight loss surgery can take place, you should be referred to your nearest specialist unit for an assessment, to see if you're a suitable candidate for surgery.


Your assessment may consist of three main phases:

  • physical assessment
  • psychological assessment
  • nutritional assessment

You should be given information on the reason for these tests, how they'll be carried out and the meaning of any results.

Physical assessment

The purpose of the physical assessment is to check whether you have any health problems or other factors that could complicate your surgery.

You may receive the following tests:

  • blood tests
  • an electrocardiograph (ECG), where electrodes are used to measure the electrical activity of your heart
  • chest X-rays
  • spirometer – a machine that measures how well you can breathe in and out
  • ultrasound scan – this uses sound waves to build up a picture of the inside of your body and is useful for spotting conditions such as gallstones and non-alcoholic fatty liver disease

Psychological assessment

The psychological assessment determines whether:

  • you have any mental health conditions or emotional problems that could prevent you sticking to your lifestyle plan after surgery
  • you've developed unhealthy patterns of eating, such as binge eating, that could cause problems after surgery
  • you have realistic expectations of what life will be like after surgery

The process of assessment can differ between units, but it's likely you'll be asked questions about:

  • how obesity is affecting your emotions
  • how obesity is affecting your relationships with others
  • how obesity is affecting your daily activities
  • whether you're currently taking medication or seeking treatment for a mental health condition
  • your current pattern of eating and your willingness to change the pattern after surgery
  • what benefits you expect surgery to bring you and how you feel your life will be after surgery

Having a mental health condition such as depression or an eating disorder doesn't automatically mean you're not suitable for surgery. However, surgery may be delayed until it's under control.

Nutritional assessment

The nutritional assessment has two main purposes.

The first is for the dietitian to obtain a detailed history of your current diet and associated patterns of eating and how these have contributed to your obesity.

The second is to ensure you fully understand the dietary commitments you will need to make after surgery, which may include:

  • improving the nutritional content of your meal
  • eating small amounts of food slowly rather than rushing through a meal as quickly as possible

Your dietitian may also recommend a calorie-controlled diet for several weeks or months before surgery. This is because losing even a modest amount of weight before surgery is known to reduce the risks of complications, especially if you're going to have keyhole surgery.

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How is it performed?

The three most widely used types of weight loss surgery are gastric banding and sleeve gastrectomy, both based on restriction, and gastric bypass, which uses a combination of restriction and malabsorption.

These operations are usually performed as a type of laparoscopic (keyhole) surgery, where a series of small incisions are made in the abdomen, rather than one large incision. The advantage of this type of surgery is it causes less pain afterwards and has a faster recovery time.

However, laparoscopic surgery may not always be possible in severely morbidly obese people, or those who have had other abdominal operations.

They are carried out under general anaesthetic, which means you'll be asleep during surgery and won't feel any pain.

The surgeon makes the incisions in your abdomen, then inserts an instrument known as a laparoscope through one of the cuts. A laparoscope is a thin, rigid tube containing a light source and a camera. The camera relays images of the inside of your abdomen to a television monitor.

Each type of surgery is discussed in more detail below.

Gastric banding

Other small instruments are placed through the cuts to place a gastric band around the top of your stomach, effectively dividing your stomach into two, leaving a small pouch at the top.

As it takes less food to fill the pouch, it takes less food to make you feel full.

The band is connected to an access port, which is placed under the skin. Saline (sterile salt water) can be passed through this port to inflate the band. This allows the band to be adjusted as required after surgery.

The surgery usually takes around an hour to complete.

Gastric bypass

Gastric bypass uses special surgical staplers to create a small pouch at the top of your stomach. This pouch is then connected directly to a section of your small intestine, bypassing the rest of the stomach and bowel.

This means it takes less food to make you feel full and you'll also absorb fewer calories from the food you eat.

Sleeve gastrectomy

During a sleeve gastrectomy, part of the stomach is removed. This restricts the amount of food that can be eaten and results in you feeling full sooner than normal when eating.

Bypass, banding or sleeve?

All three types of surgery have advantages and disadvantages.

There's usually more weight loss after a gastric bypass and sleeve gastrectomy than after a gastric band.

Most people with a gastric band lose around half their excess body weight, whereas most people with a gastric bypass or sleeve gastrectomy lose around two-thirds of their excess body weight.

However, because it's more technically demanding, a gastric bypass carries a higher risk of complications, including death. Read about the risks of weight loss surgery.

A gastric band is reversible, so if you find it difficult to cope with the restrictions associated with life after surgery, you can have the band removed.

A gastric bypass or a sleeve gastrectomy, on the other hand, can't be reversed. You'll also be required to take nutritional supplements for the rest of your life if you have a gastric bypass.

A gastric bypass often has a much greater impact on type 2 diabetes, in a shorter time, than either a gastric band or sleeve gastrectomy.

Discuss the advantages and disadvantages of both types of surgery with your surgical team.

Other types of bariatric surgery

Other types of weight loss surgery, which are less commonly used, are outlined below.

Bilo-pancreatic diversion

A bilo-pancreatic diversion is similar to a gastric bypass, except a much larger section of the small intestine is bypassed, meaning you'll absorb even fewer calories from the food you eat.

A bilo-pancreatic diversion can achieve a good level of weight loss (up to 80% of excess body weight) but it carries a high risk of complications and can cause unpleasant side effects, such as unpleasant-smelling diarrhoea.

Because of this, a bilo-pancreatic diversion is usually only recommended when it's felt that rapid weight loss is required to prevent a serious health condition, such as heart disease, from getting worse.

Intra-gastric balloon

An intra-gastric balloon is a soft silicone balloon that's surgically implanted into your stomach. The balloon is filled with air or saline solution (sterile salt water), and so takes up some of the space in your stomach. This means you don't need to eat as much before you feel full.

This procedure is only temporary, and the balloon is usually removed after six months. The procedure is useful if you don't meet the criteria for the other types of surgery – for example, because you're too obese.

An intra-gastric balloon procedure can usually be done without making an incision in your abdomen. Instead, the balloon can be passed through your mouth and down into your stomach using an endoscope (a thin, flexible tube that has a light and a camera on one end).

Read more information about a gastroscopy.

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After weight loss surgery, you will need a few days to recover. It may also be several weeks or months before you can resume normal activities, depending on the type of surgery you have.

Recovering from a gastric band operation

When you wake after surgery, you will probably have some pain at the site of the surgery. This is normal and should pass within a few days.

Blood clots are an uncommon but serious complication that can occur after banding, including:

To reduce the risk of blood clots, you may be given a blood-thinning medication, such as heparin, and compression stockings to wear.

Once you feel well enough, move around as much you can as this will further reduce your risk of blood clots.

For the first 24 hours, you will only be allowed to drink a small amount of liquid to prevent vomiting..

Gradually, small amounts of solid food will be introduced into your diet. For more information, see Weight loss surgery - recommendations.

Gastric band surgery may be carried out as a day case and most people are well enough to leave hospital within 24 hours of surgery. You can resume normal activities within four to six weeks.

Four to six weeks after surgery, your stomach should have healed enough that your band can be adjusted by inflating it with saline (sterile salt water).

This is done by inserting a needle via the access point through which the saline is pumped. The band will then inflate and constrict the upper pouch of your stomach. The whole process takes around 15 minutes. This is sometimes done after numbing your abdomen with a local anaesthetic, using an X-ray to locate the band.

Often, this process of adjustment is a fine balancing act. For example, if the band is too loose you may not lose weight, but if the band is too tight, you may vomit after eating.

Therefore, it can take a number of sessions before the ideal adjustment for your band is reached.

Recovering from a gastric bypass

Once you wake after surgery, you will probably have a drip in your arm, to provide your body with liquids, and a tube in your bladder, known as a urinary catheter, to drain urine out of your bladder.

These tubes will be removed once you are well enough to get out of bed.

Again, you may be given blood-thinning medication and compression stockings to wear to help prevent blood clots.

You will only be allowed a liquid diet immediately after surgery, and solids will be slowly introduced into your diet.

Most people are well enough to leave hospital one to four days after surgery and resume normal activities within three to five weeks.

Recovering from other types of weight loss surgery

The recovery time for other types of weight loss surgery are:

  • sleeve gastrectomy - one to four days to leave hospital and four to six weeks to resume normal activities
  • bilo-pancreatic diversion - one to four days to leave hospital and three to six months to resume normal activities
  • gastric balloon - fitting a gastric balloon is a non-invasive procedure (does not involve making incisions in your body), so you should be able to leave hospital on the same day and resume normal activities almost immediately

You'll also only be allowed a liquid diet immediately after these types of surgery, and solids will be slowly introduced into your diet.

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It is very important that you stick to your recommended diet plan after your surgery.

Diet plans can differ between specialist centres and depending on your individual circumstances, but most people will be given a plan similar to the ones described below.

Diet after a gastric band operation

Your diet after a gastric band operation will progress over three main stages:

  • In the first four weeks after surgery, you will only be able to drink liquids and eat small amount of puréed food, such as mashed potato.
  • In weeks four to six, you can you have soft food, such as chicken.
  • After six weeks, gradually resume a healthy diet based on eating small amounts of nutritional food.

Each stage is discussed in more detail below.

First four weeks

It is very important that any food you eat during this period is puréed. Attempting to eat solid foods at this stage could put pressure on the band and damage it.

Puréed food has the same texture and consistency of baby food. You can purée food using a food processor, hand-held blender or potato masher.

Additional fluids, such as sauces or water, may be required to soften some types of food.

Aim to eat small portions four to five times a day. A portion is around 100g or 5-6 tablespoons of food. Eat all your meals slowly, taking small mouthfuls.

Stop eating as soon as you feel full. Because of the position of the band, you will probably experience a feeling of fullness or tightness in your chest rather than in your stomach.

Aim to drink around 1.5 litres (2.5 pints) of water a day. Drink small glasses, around 100-200ml, between meals but never with your meals.

If you experience repeated episodes of vomiting after eating, it may be a sign that you are eating too much or that your band needs to be adjusted. Contact your surgical unit for advice.

Weeks four to six

Continue to eat a similar diet as you did for the first four weeks, but your food no longer has to be puréed, although it should be soft.

For example, you could eat:

  • wholewheat breakfast cereals mixed with milk
  • porridge
  • mashed potatoes and melted cheese
  • soup
  • yoghurt
  • rice pudding

After six weeks

After six weeks, you will be ready to adopt a long-term diet that you will need to stick to for the rest of your life. Your band should now be adjusted correctly so you should need to eat much less to satisfy your appetite.

While weight loss is an important goal of your diet, do not neglect the nutritional content of your diet. See below, for more information on what makes a healthy, balanced diet.

The British Obesity Surgery Patient Association (BOSPA), a charity for people who could benefit from surgery, recommends that to get the most benefit from your gastric band, you need to follow six golden rules:

  • Only eat three meals a day.
  • Avoid snacking between meals. If you are following your recommended guidelines, there is no reason why you should feel hungry between meals.
  • Eat solid food. While soft foods may be easier to digest, they usually contain more carbohydrates and fat and make you feel less full than solid foods.
  • Eat slowly and stop eating as soon as you feel full. Cut your food into very small chunks, then chew each chunk as many times as possible before swallowing. Stop eating once you feel a sensation of fullness or tightness in your chest. Overeating or eating too fast could cause unpleasant symptoms, such as pain and vomiting.
  • Do not drink during meals. This can flush food out of your stomach pouch and make you feel less full. Avoid drinking fluids 30 minutes before a meal and for an hour afterwards.
  • Avoid drinking high-calorie drinks, such as cola, alcohol, sweetened fruit juices and milkshakes. These types of drink will quickly pass out of your stomach and into your small intestine, increasing your calorie intake. Ideally, drink water or zero-calorie drinks, such as diet cola or diet lemonade.

Diet after a gastric bypass

The progression of diet stages after a gastric bypass is broadly similar to those after a gastric band:

  • In the first week after surgery, only drink liquids (this doesn't include puréed food).
  • In weeks two to four, you can eat puréed food in the same quantities (100g) and frequencies (four to five times a day) as described above.
  • In weeks four to six, you can eat soft food.
  • After six weeks, gradually resume eating a healthy diet.

The golden rules above also apply to your diet after a gastric bypass.

However, you need to be aware of several additional issues.

Firstly, you'll need to avoid eating food high in sugar, such as chocolate, cakes, sweets and biscuits. This is because your bypass affects how you digest sugar, and any sugar you eat will trigger your body to produce high levels of insulin.

The excessive amount of insulin can cause a number of unpleasant symptoms that are collectively known as dumping syndrome. Symptoms of dumping syndrome include:

  • nausea
  • abdominal (tummy) pain
  • diarrhoea
  • light-headedness

Secondly, you'll need to take daily vitamin and mineral supplements, as your small intestine will no longer be able to digest all the vitamins and minerals your body needs from your diet.

The dosage and type of supplements can vary from case to case, but most people are required to take:

  • a multivitamin supplement, which contains a combination of different vitamins
  • a calcium supplement (the body requires calcium to maintain healthy bones)
  • an iron supplement

Diet after other types of weight loss surgery

The recommended diet after other types of weight loss surgery is likely to be similar to the advice above.

Your specialist centre will be able to provide more detailed advice.

Exercise after weight loss surgery

Losing weight and then maintaining a healthy weight doesn't simply involve reducing the amount of calories you eat. Burning calories while exercising is also important.

Regular exercise has additional health benefits other than weight loss. These include reducing your risk of developing heart disease and some types of cancer, and boosting your self-esteem and wellbeing.

You'll probably be given an exercise plan that starts gradually with low to moderate amounts of physical exercise, such as 10 minutes a day, then gradually increasing.

The exercise should be intense enough to leave you feeling out of breath and getting your heart beating faster.

Recommended types of physical exercise include:

  • activities that can be incorporated into everyday life, such as brisk walking, gardening or cycling
  • supervised exercise programmes
  • activities such as swimming, walking (where you aim to walk a certain number of steps a day) and stair climbing

Chose physical activities that you enjoy as you'll be more likely to continue doing them..

A healthy balanced diet

What you eat is just as important as how much you eat after your surgery.

Generally, your diet should contain a healthy mix of the five main food groups:

  • protein – ideally low-fat protein foods such as chicken, fish, eggs and beans
  • dairy products – such as skimmed milk and low-fat cheese and yogurt
  • carbohydrates – such as bread, potatoes and cereals
  • fruit and vegetables – ideally five portions a day
  • fats – using a small amount of olive oil when cooking should provide your body with all the fat it needs

Your specialist centre can give you more advice on how best to meet your individual nutritional needs.

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As long as you stick to the recommendations on diet and exercise, all types of weight loss surgery can achieve good and often impressive results.

However, rapid weight loss can cause complications. See Weight loss surgery - risks for more information.

Gastric band

A person with a gastric band should expect to lose 50% of their excess body weight within two years.

The weight loss is a gradual process with:

  • 35% of excess weight lost within six months of surgery
  • 40% of excess weight lost by 12 months
  • 50% of excess weight lost by 24 months

Also expect to see a marked improvement in health conditions related to obesity, particularly:

Most people also report an improvement in their overall quality of life in terms of:

  • day-to-day pain and discomfort
  • general physical health
  • mental health

Gastric bypass

A person with a gastric bypass should expect to lose 70% of their excess body weight within two years.

The weight loss tends to be more rapid in the first year (60% of the excess weight lost) then slows in the second year, with only an additional 10% weight loss.

Again, expect to see a marked improvement in the health conditions above.

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The rapid weight loss associated with weight loss surgery can cause a number of side effects and has a number of risks. These are outlined below.

Complications immediately after surgery

Complications that can occur during or immediately after surgery include:

  • infection - this affects around 1 in 20 people
  • blood clots in the legs (deep vein thrombosis) or lungs (pulmonary embolism) - this affects around 1 in 100 people
  • internal bleeding - this affects around 1 in 100 people

Excess skin

While weight loss surgery can successfully remove the fat in the body, it cannot cause skin to revert to its pre-obesity tightness and firmness.

Therefore, if you were obese, especially for many years, you may be left with excess folds and rolls of skin, particularly around the breasts, tummy, hips and limbs.

These folds and rolls normally become most apparent 12-18 months after surgery. They can look ugly and are difficult to keep clean, so you may be vulnerable to developing rashes and infections.

Cosmetic surgery can be used to remove the excess skin. However, as this treatment is for cosmetic and not clinical reasons, it is not available on the NHS.

The price for a course of skin-removal treatment can range from £1,500 to £6,000 depending on the amount of skin that needs to be removed.

For more information, see the topic on Cosmetic surgery.


Around 1 in 12 people will develop gallstones after weight loss surgery, typically 10 months after surgery.

Gallstones are small stones, usually made of cholesterol, that form in the gallbladder.

In most cases, gallstones do not cause any symptoms. However, if they become trapped in a duct (an opening or channel), they can irritate and inflame the gallbladder and cause symptoms, such as:

  • a sudden intense pain in your abdomen (tummy)
  • nausea and vomiting
  • jaundice (yellowing of the skin and the whites of the eyes)

Psychosocial effects of surgery

While most people who undergo weight loss surgery report an improvement in their quality of life, several psychosocial effects may be related to rapid weight loss.

Some people have reported relationship problems with their partner as their partner begins to feel nervous, anxious or possibly jealous about their weight loss.

Social occasions that revolve around food, such as family meals, can become awkward, as it's common to feel self-conscious about your reduced capacity to eat.

It's also common for a person to experience a worsening of mood when their weight stabilises, typically two years after surgery. This is often because many people realise that problems that existed before surgery, such as money worries or difficulties at work, are still there.

You may find it useful to discuss these issues with people who have also had weight loss surgery. The British Obesity Surgery Patient Association’s website contains a service directory of support groups in the UK.

Read more information and tips for dealing with psychosocial effects of surgery, such as stress, anxiety or depression..

Stomal stenosis

A common complication in people with a gastric bypass is that the hole (stoma) connecting their stomach pouch to their small intestine becomes narrowed and may get blocked by a piece of food. This is known as stomal stenosis and is thought to occur in one-fifth of people with a gastric bypass.

The most common symptom of stomal stenosis is persistent vomiting.

Stomal stenosis can be treated by directing a small flexible tube, known as an endoscope, to the site of the stoma. A balloon attached to the endoscope is inflated to unblock the stoma.

The best way to prevent stomal stenosis is to always cut food into small chunks, chew the chunks thoroughly and avoid drinking during meals, see Weight loss surgery - recommendations.

Gastric band slippage

Gastric band slippage is a complication that affects around 1 in 50 people with a gastric band.

As the name suggests, the band slips out of position. This means that the stomach pouch becomes bigger than it should be. This can cause symptoms such as:

  • heartburn
  • nausea
  • vomiting

Further surgery will be required to repair the band.

Food intolerance

Around 1 in 35 people with a gastric band develop a food intolerance, often many years after their surgery.

A food intolerance is when your body is unable to tolerate certain foods, such as red meat or green salad, resulting in a number of unpleasant symptoms such as:

The reason why a food intolerance can develop after surgery is unclear.

In most cases, avoiding foods that trigger a reaction should help improve symptoms, but if you have persistent symptoms associated with a number of different foods, it may be necessary to remove the band and replace it with a gastric bypass.


No surgery is entirely safe and all surgical procedures carry a risk of death. However, the outlook for weight loss surgery has greatly improved with modern techniques.

The risk of death in hospital after having any kind of weight loss surgery is around 1 in 1,000.

Complications of weight loss surgery that could lead to death include:

A number of risk factors have been identified that increase the risk of death during or shortly after weight loss surgery. These are:

  • being aged over 45 years old
  • high blood pressure
  • having a BMI of 50 or above
  • being male, as obese men tend to weigh more than obese women
  • having a known risk factor for a pulmonary embolism

Known risk factors for a pulmonary embolism include:

  • having a previous history of blood clots
  • pulmonary hypertension, when the blood pressure inside your lungs is particularly high
  • obesity hypoventilation syndrome, when you have persistent breathing difficulties related to your obesity

The risk factors above can have a significant impact on your individual risk of death. However, untreated obesity, especially morbid obesity, carries a significant risk of premature death itself.

In most cases, the benefits of surgery outweigh the risks in people who meet the criteria for weight loss surgery.

For more information, see Weight loss surgery - who can use it?

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The information on this page has been adapted by NHS Wales from original content supplied by NHS Choices.
Last Updated: 19/05/2015 10:02:44